Anaerobic degradation of monochlorinated phenols and monochlorinated benzoates by a variety of aquatic sediments was compared under four enrichment conditions. A broader range of compounds was degraded in enrichments inoculated with sediment exposed to industrial effluents. Methanogenic and 1 mM BESA-amended enrichments were most likely, while nitrate and sulfate enrichments least likely, to degrade the compounds tested. Chlorophenols were more readily degraded than chlorobenzoates. However, 2-chlorophenol, 3-chlorophenol, and 3-chlorobenzoate degradation was observed most often and with equal frequency. Para chlorinated compounds were least likely to be degraded. A relative order of ortho < meta < para was observed for onset of chlorophenol degradation, while the order for chlorobenzoate degradation was meta < ortho < para. In laboratory transfers, 2- and 3-chlorobenzoate degradation was most easily maintained, while degradation of para chlorinated compounds was least stable. (Copyright (c) 1989 American Society for Microbiology.)